Manufacturers' tests of procedures to clean medical scopes linked with ''superbug'' outbreaks contained flaws that render their cleaning instructions unreliable, according to a senior official with the U.S. Food and Drug Administration.

The scopes were linked to the exposure of 179 patients to drug-resistant bacteria at UCLA's Ronald Reagan Medical Center in Los Angeles and may have contributed to two deaths. Those incidents were announced last month.

In early 2014, following a superbug outbreak at a hospital in Illinois, the FDA asked Fujifilm Holdings Corp, Olympus Corp and Pentax, which make the devices, to submit their test results for review, Dr. Stephen Ostroff, the agency's chief scientist, said in an interview.

In some cases the tests were poorly carried out. In others, they were properly conducted but the cleaning and disinfecting protocol failed, said Ostroff, who will become the FDA's acting commissioner when Dr. Margaret Hamburg leaves at the end of March.

The deficiencies in the companies' tests has not been reported.

The flawed data calls into question the reliability of all current cleaning and disinfecting protocols and expose a weakness in the FDA's regulation of such devices - one which the agency is now moving to close.

The FDA has said that even when hospitals adhered to the manufacturers' instructions for cleaning scopes, patients have contracted multidrug-resistant bacterial infections from the devices, but the agency had not detailed manufacturers' tests of their own procedures.

Under guidance issued in 1996, companies making duodenoscopes did not have to submit data, but merely attest that cleaning protocols used in their own studies were effective. The companies set their own standards for effectiveness.

After the Illinois outbreak, the FDA said it would require duodenoscope manufacturers to provide underlying test data at the time they apply for marketing approval. And it has imposed specific benchmarks by which effectiveness should be measured.

Among those benchmarks: the agency expects to see the elimination of 99.9999 percent of microbes at each of several locations on the scope.

''We have set a higher bar to demonstrate adequate validation than was expected in the past based on evolving science and experiences with more recent outbreaks,'' Ostroff said. ''What was acceptable a few years ago is not adequate today.''

A spokeswoman for Fujifilm, Diane Rainey, said it is working with the FDA to evaluate and respond to concerns about contamination concerns associated with the instruments and that patient safety ''is, and always will be, Fujifilm's primary consideration.''

Representatives from Pentax and Olympus did not respond to requests for comment after business hours on Sunday.

Advisory committee meeting

Ostroff told Reuters the FDA plans to convene a panel of outside scientific advisors to review the safety of the devices ''to put all the available information on the table and have a discussion about it.''

The FDA's advisory committees counsel the agency on a variety of scientific and regulatory issues, including drug and device approvals and safety matters. The agency is not required to follow recommendations made by its advisors, but typically does so.

No date has been set for the meeting, which will be public, Ostroff said.

The problems the advisory committee will likely be asked to consider do not appear easy to fix.

The companies still have not come up with validated cleaning and disinfecting protocols. The FDA found initial data submitted by the companies inadequate and asked them to test the protocols again using a more robust methodology. Those results were also unsatisfactory.

They have been asked to try again, and the process will continue until a reliably safe protocol is found, Ostroff said.

Duodenoscopes are threaded through the mouth, throat and stomach to the top of the small intestine and are used to drain fluid from pancreatic and biliary ducts. They have been associated with episodic infections for more than a decade, but those infections could often be treated with antibiotics.

That is no longer always the case. An increasing number of bacteria are resistant to drugs, including a family of germs known as carbapenem-resistant Enterobacteriaceae, or CRE, the bacteria implicated in the outbreak announced last month at UCLA and the 2013 outbreak at Advocate Lutheran General Hospital near Chicago.

In addition to prompting the FDA to ask companies to submit their underlying validation data, the Illinois outbreak prompted the agency to examine the design of the devices. Its assessment is ongoing but has already raised red flags, Ostroff said.

It is far from clear whether design changes would be effective: companies have modified the devices before with no discernible results.

In 2004 Fujifilm received FDA clearance for a change that would seal an open channel in the device to keep out bodily fluids. In 2009, the FDA cleared a similar change by Pentax.

Olympus, whose devices were used in the UCLA outbreak, made the change in 2010, though it did not file for FDA clearance until last October after being notified about the omission by the agency. The application has not yet received clearance, but Ostroff said the FDA has not removed the device from the market because doing so could create a shortage.